The present invention is directed generally to the coating arts, and more particularly to a novel and improved non-contact coating apparatus for applying a coating to a moving surface.
While the invention may find utility in other applications, the disclosure will be facilitated by specific reference to the problem of application of a liquid glue medium in a desired pattern to a moving substrate such as a paper carton. In the manufacture of folded paper cartons and the like it is desirable to apply lines or beads of glue to predetermined surfaces of the folded carton and in predetermined patterns for use in later erecting and assembling the carton.
In non-contact gluing methods, a controllable extruding applicator or glue-dispensing mechanism is utilized, spaced some distance above the surface of the moving carton or other workpiece on which glue is to be applied in a desired pattern. Generally speaking, such a pattern comprises one or more relatively straight lines of glue of predetermined length. Multiple lines of glue may, of course, be applied by the use of multiple nozzles or glue dispensers aligned with appropriate portions of the workpiece or carton surface. Non-contact extrusion gluing systems of this type are discussed in prior U.S. Pat. Nos. 4,408,562 and 4,527,510, both commonly owned with this application, and to which further reference is invited.
While the non-contact extrusion gluing systems of the above-referenced U.S. patents have proven highly reliable in operation, there is room for further improvement. More specifically, in some high-volume, high-speed gluing systems, some build-up of glue on and about the nozzle or outlet of the dispenser or applicator member has been experienced. While this may be corrected by physical wiping or cleaning by an operator, it is quite difficult to correct this condition while the gluing system is in operation. At the relatively high speeds at which most systems are operated, it is quite difficult for an operator to physically wipe or otherwise clean the dispensing applicator or nozzle without interfering with the relatively high speed dispensing of glue thereby. However, it is also undesirable to shut down a relatively high speed, and highly efficient gluing system and attendant article handling lines and equipment at frequent intervals to achieve such cleaning or wiping operations.
Similarly, when the gluing apparatus is turned off for some period of time, there is a tendency for glue residue in and about the outlet and outlet valve component to dry and harden. We therefore propose a system which will also cover the glue outlet when the system is shut down to prevent such drying and hardening.